bug#55857: Odd Shepherd message on 'guix system reconfigure': (map (# ?) ?)

[Maxim Cournoyer]

Hi Ludo,

This bug was closed as notabug, but I still see it as an issue worth
fixing.  Just using the (gnu services herd) API to query live services
ends up producing such a messages; I think from the 'resolve-transients'
procedure there that calls to eval-there unconditionally.

Perhaps the shepherd output could be redirected to /dev/null at that
specific place to avoid noisy output such as:

--8<---------------cut here---------------start------------->8---
2023-05-18 23:15:00 22491 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: running...
2023-05-18 23:15:00 22491 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: shepherd: 
Evaluating user expression (and (defined? (quote transient?)) (map (# ?) ?)).
2023-05-18 23:15:00 22491 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: completed 
in 0.029s
2023-05-18 23:20:00 22804 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: running...
2023-05-18 23:20:00 22804 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: shepherd: 
Evaluating user expression (and (defined? (quote transient?)) (map (# ?) ?)).
2023-05-18 23:20:00 22804 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: completed 
in 0.039s
2023-05-18 23:25:00 23849 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: running...
2023-05-18 23:25:00 23849 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: shepherd: 
Evaluating user expression (and (defined? (quote transient?)) (map (# ?) ?)).
2023-05-18 23:25:00 23849 
/gnu/store/zmb73m7qgqagpb4vjhdd9jgkwp716p0m-wireguard-wg0-monitoring: completed 
in 0.028s
--8<---------------cut here---------------end--------------->8---

The above output is triggered by this code [0].

[0]  https://issues.guix.gnu.org/63402#13-lineno225

-- 
Thanks,
Maxim